A catalytic converter supporting a catalyst capable of purifying exhaust gas is disposed in the route of an exhaust pipe in order to purify harmful substances contained in exhaust gas discharged from an engine.
To enhance the efficiency of the catalytic converter to purify harmful substances, the temperate inside the catalytic converter must be maintained at a temperature suitable for catalyst activation (hereinafter also referred to as catalyst activation temperature).
In the case of a vehicle not provided with a means that directly heats a catalyst carrier constituting the catalytic converter, the temperature of exhaust gas is low immediately after the vehicle starts running, so that the temperature inside the catalytic converter does not reach the catalyst activation temperature, making it difficult to effectively prevent discharge of harmful substances.
In addition, in the case of a hybrid vehicle not provided with a means that directly heats the catalyst carrier, the temperature inside the catalytic converter decreases while the motor is driven and the engine is stopped, and in some cases, the temperature inside the catalytic converter is lower than the catalyst activation temperature. Also in this case, it is difficult to effectively prevent discharge of harmful substances.
In order to solve these problems, for example, Patent Literature 1 discloses an invention in which the catalyst carrier itself is used as a heating element that generates heat by energization, and the temperature inside the catalytic converter is increased, if necessary, to or above the temperature of the catalyst activation temperature.